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Adoptive cell transfer (ACT) immunotherapy has remarkable efficacy against some hematologic malignancies. However, its efficacy in solid tumors is limited by the adverse tumor microenvironment (TME) conditions, most notably that acidity inhibits T and natural killer (NK) cell mTOR complex 1 (mTORC1) activity and impairs cytotoxicity. In several reported studies, systemic buffering of tumor acidity enhanced the efficacy of immune checkpoint inhibitors. Paradoxically, we found in a MYC–driven hepatocellular carcinoma model that systemic buffering increased tumor mTORC1 activity, negating inhibition of tumor growth by anti-PD1 treatment. Therefore, in this proof-of-concept study, we tested the metabolic engineering of immune effector cells to mitigate the inhibitory effect of tumor acidity while avoiding side effects associated with systemic buffering. We first overexpressed an activated RHEB in the human NK cell line NK-92, thereby rescuing acid-blunted mTORC1 activity and enhancing cytolytic activity. Then, to directly mitigate the effect of acidity, we ectopically expressed acid extruder proteins. Whereas ectopic expression of carbonic anhydrase IX (CA9) moderately increased mTORC1 activity, it did not enhance effector function. In contrast, overexpressing a constitutively active Na+/H+-exchanger 1 (NHE1; SLC9A1) in NK-92 did not elevate mTORC1 but enhanced degranulation, target engagement, in vitro cytotoxicity, and in vivo antitumor activity. Our findings suggest the feasibility of overcoming the inhibitory effect of the TME by metabolically engineering immune effector cells, which can enhance ACT for better efficacy against solid tumors. Significance: This study demonstrates the feasibility of metabolic engineering immune effector cells to overcome inhibition in the TME, an approach that could enhance the efficacy of adoptive transfer immunotherapy.

Adoptive cell transfer (ACT) immunotherapy has remarkable efficacy against some hematologic malignancies. However, its efficacy in solid tumors is limited by the adverse tumor microenvironment (TME) conditions, most notably that acidity inhibits T and natural killer (NK) cell mTOR complex 1 (mTORC1) activity and impairs cytotoxicity. In several reported studies, systemic buffering of tumor acidity enhanced the efficacy of immune checkpoint inhibitors. Paradoxically, we found in a MYC–driven hepatocellular carcinoma model that systemic buffering increased tumor mTORC1 activity, negating inhibition of tumor growth by anti-PD1 treatment. Therefore, in this proof-of-concept study, we tested the metabolic engineering of immune effector cells to mitigate the inhibitory effect of tumor acidity while avoiding side effects associated with systemic buffering. We first overexpressed an activated RHEB in the human NK cell line NK-92, thereby rescuing acid-blunted mTORC1 activity and enhancing cytolytic activity. Then, to directly mitigate the effect of acidity, we ectopically expressed acid extruder proteins. Whereas ectopic expression of carbonic anhydrase IX (CA9) moderately increased mTORC1 activity, it did not enhance effector function. In contrast, overexpressing a constitutively active Na+/H+-exchanger 1 (NHE1; SLC9A1) in NK-92 did not elevate mTORC1 but enhanced degranulation, target engagement, in vitro cytotoxicity, and in vivo antitumor activity. Our findings suggest the feasibility of overcoming the inhibitory effect of the TME by metabolically engineering immune effector cells, which can enhance ACT for better efficacy against solid tumors.Significance:This study demonstrates the feasibility of metabolic engineering immune effector cells to overcome inhibition in the TME, an approach that could enhance the efficacy of adoptive transfer immunotherapy.

Supplementary Fig. S1. CA9 fails to enhance the cytolytic activity of NK-92 cells in vitro. Supplementary Fig. S2. NHE1 enhances in vitro cytotoxicity of NK-92 cells without affecting proliferation or survival. Supplementary Fig. S3. Representative three-dimensional (3D) reconstruction of confocal microscopic images of antibody-activated NK-92. Supplementary Fig. S4. NHE1 increases the protein expression of c-Myc in NK-92 cells. Supplementary Fig. S5. NHE1 enhances in vitro cytotoxicity of NK-92MI. Supplementary Table S1. Nucleotide sequence of codon-optimized, constitutively active human NHE1 cDNA. Supplementary Table S2. Differentially expressed genes between Na+/H+-exchanger 1 (NHE1)-expressing and empty vector NK-92 cells, ranked by log2(fold change).

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Tables of proteomics and CD4/8 staining

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Metastatic melanoma is challenging to clinically address. Although standard-of-care targeted therapy has high response rates in patients with BRAF-mutant melanoma, therapy relapse occurs in most cases. Intrinsically resistant melanoma cells drive therapy resistance and display molecular and biologic properties akin to neural crest-like stem cells (NCLSC) including high invasiveness, plasticity, and self-renewal capacity. The shared transcriptional programs and vulnerabilities between NCLSCs and cancer cells remains poorly understood. Here, we identify a developmental LPAR1-axis critical for NCLSC viability and melanoma cell survival. LPAR1 activity increased during progression and following acquisition of therapeutic resistance. Notably, genetic inhibition of LPAR1 potentiated BRAFi ± MEKi efficacy and ablated melanoma migration and invasion. Our data define LPAR1 as a new therapeutic target in melanoma and highlights the promise of dissecting stem cell–like pathways hijacked by tumor cells.Significance:This study identifies an LPAR1-axis critical for melanoma invasion and intrinsic/acquired therapy resistance.

Supplementary Figures

Time-lapse imaging of A375(Fucci2)-BR cells treated with the control.

A file containing supplementary figures 1-8 and the supplementary table S1.

Table S1 Mean density values of crystal violet staining of 16 melanoma cell lines treated with 6-thio-dG and PLX4720. Table S2 RNA-seq data related to A375 cells treated with 6-thio-dG. Table S3 RNA-seq data related to A375 cells treated with BIBR 1532. Table S4 Apoptotic index and ssGSEA scores of 11 gene sets in 18 CCLE melanoma cell lines. Table S5 RPPA data related to A375 cells treated with 6-thio-dG. Table S6 Mean density values of crystal violet staining of 6 therapy-resistant melanoma cell lines treated with 6-thio-dG. Table S7 RPPA data related to the comparison between LOX-IMVI parental and BR cells. Table S8 RPPA data related to LOX-IMVI parental cells treated with 6-thio-dG. Table S9 RPPA data related to LOX-IMVI BR cells treated with 6-thio-dG. Table S10 RPPA data related to LOX-IMVI BR xenografts treated with 6-thio-dG. Table S11 The clinical information from patients with metastatic melanoma treated with immunotherapies.

Supplementary Materials

Purpose: Although 67% of high-grade serous ovarian cancers (HGSOC) express the estrogen receptor (ER), most fail antiestrogen therapy. Because MAPK activation is frequent in ovarian cancer, we investigated if estrogen regulates MAPK and if MEK inhibition (MEKi) reverses antiestrogen resistance.Experimental Design: Effects of MEKi (selumetinib), antiestrogen (fulvestrant), or both were assayed in ER-positive HGSOC in vitro and in xenografts. Response biomarkers were investigated by gene expression microarray and reverse phase protein array (RPPA). Genes differentially expressed in two independent primary HGSOC datasets with high versus low pMAPK by RPPA were used to generate a “MAPK-activated gene signature.” Gene signature components that were reversed by MEKi were then identified.Results: High intratumor pMAPK independently predicts decreased survival (HR, 1.7; CI > 95%,1.3–2.2; P = 0.0009) in 408 HGSOC from The Cancer Genome Atlas. A differentially expressed “MAPK-activated” gene subset was also prognostic. “MAPK-activated genes” in HGSOC differ from those in breast cancer. Combined MEK and ER blockade showed greater antitumor effects in xenografts than monotherapy. Gene set enrichment analysis and RPPA showed that dual therapy downregulated DNA replication and cell-cycle drivers, and upregulated lysosomal gene sets. Selumetinib reversed expression of a subset of “MAPK-activated genes” in vitro and/or in xenografts. Three of these genes were prognostic for poor survival (P = 0.000265) and warrant testing as a signature predictive of MEKi response.Conclusions: High pMAPK is independently prognostic and may underlie antiestrogen failure. Data support further evaluation of fulvestrant and selumetinib in ER-positive HGSOC. The MAPK-activated HGSOC signature may help identify MEK inhibitor responsive tumors. Clin Cancer Res; 22(4); 935–47. ©2015 AACR.

A file containing RPPA and RNAseq datasets, pathway analyses and prediction calculations presented in the main figures.

Purpose: Telomerase promoter mutations are highly prevalent in human tumors including melanoma. A subset of patients with metastatic melanoma often fail multiple therapies, and there is an unmet and urgent need to prolong disease control for those patients.Experimental Design: Numerous preclinical therapy-resistant models of human and mouse melanoma were used to test the efficacy of a telomerase-directed nucleoside, 6-thio-2′-deoxyguanosine (6-thio-dG). Integrated transcriptomics and proteomics approaches were used to identify genes and proteins that were significantly downregulated by 6-thio-dG.Results: We demonstrated the superior efficacy of 6-thio-dG both in vitro and in vivo that results in telomere dysfunction, leading to apoptosis and cell death in various preclinical models of therapy-resistant melanoma cells. 6-thio-dG concomitantly induces telomere dysfunction and inhibits the expression level of AXL.Conclusions: In summary, this study shows that indirectly targeting aberrant telomerase in melanoma cells with 6-thio-dG is a viable therapeutic approach in prolonging disease control and overcoming therapy resistance. Clin Cancer Res; 24(19); 4771–84. ©2018 AACR.See related commentary by Teh and Aplin, p. 4629

Supplementary materials and methods

Supplementary Figure 1. (A) Percent of HGSOCs from the TCGA cohort with mutations in 42 genes associated with the RAS/Raf/MEK/MAPK pathway (N=45/311); (B) Percent of HGSOCs from the TCGA cohort with copy number amplifications or mRNA overexpression of 42 MAPK pathway genes (N=232/311) Supplementary Figure 2. (A); Percent of high-pMAPK and low-pMAPK HGSOCs as defined by RPPA from the TCGA cohort with (A) copy number amplification (B) mRNA overexpression, (C) mutation in which MAPK pathway genes are genetically activated in hMAPK cancers. The numbers with data available for each analysis in TCGA are shown below graphs. Supplementary Figure 3. Dose dependent effects of selumetinib on ER positive, MAPK kinase activated ovarian cancer cells Supplementary Figure 4. In vitro cell cycle effects of MEK and ER inhibition on ER+ BG-1 OVCA cells Supplementary Figure 5: Gene expression changes expressed as log fold change over baseline control untreated cell values after 48 hours of treatment with fulvestrant (1 μM), selumetinib (200 nM) or both, in vitro of representative genes in (A) ER target gene expression (B) Cell signaling pathways (C) Cell cycle pathways. Supplementary Figure 6. Heat map representation of selected triplicate repeat RPPA data from PEO1-R cells treated with either monotherapy fulvestrant (FULV), selumetinib (MEK I) or dual therapy as indicated. Heat map demonstrates inter-sample variability in triplicate repeat assays. Supplementary Table 1. List of genes in the 126 gene MAPK activation profile common to the TCGA and JAPAN cohorts. Supplementary Table 2. Differences in gene mutation, overexpression and amplification between low and high pMAPK HGSOC as defined by RPPA in TCGA cohort Supplementary Table 3.Analysis of xenograft growth rates reveal synergy between fulvestrant and selumetinib therapy on OVCA PEOIR xenograft growth

Supplementary Fig. 1: Related to Fig. 2 (A) The percentage of apoptotic and dead cells indicated as PSVue 643+ cells in each of 12 BRAF-mutant melanoma cell lines treated with PLX4720 or 6-thio-dG at indicated doses for 120 hours. Cells were then harvested and co-stained with PSVue643 and Propidium iodide (PI). The average of 2 biological replicates was plotted. (B) SA-β-gal staining of 4 BRAF-mutant melanoma cell lines treated with 6-thio-dG at 5μM for 9 days. A representative image of 3 biological replicates was shown for each experimental sample. (C and D) Mouse weights of 1205Lu (C) and A375 (D) xenografts in each treatment group were shown. upplementary Fig. 2: Related to Fig. 4 (A) Long-term cell growth assay of 4 melanoma cell lines that acquired resistance to MAPKi treated with 6-thio-dG at indicated doses for 12 days. Cells were then fixed and stained with 3 crystal violet. A representative image of 2 biological replicates was shown for each experimental condition. (B-D) Tumor volumes of WM9 BR (B), UACC-903 BR (C) and A2058 CR (D) xenografts that were treated with the vehicle control and 6-thio-dG at indicated doses. (E) The ssGSEA plot of 11 MSigDB gene sets related to telomere and telomerase that were significantly altered in LOX-IMVI BR cells treated with BIBR 1532 (BIBR) or 6-thio-dG (6dG). (F-I) The heatmaps of RPPA data depicting 30 proteins that were most significantly down-regulated in four representative BR cell lines treated with 6-thio-dG, including A375 BR (F), WM3936-1 (G), 1205Lu BR (H) and WM1552C BR (I). (J) Western blotting of proteins that were downregulated in LOX-IMVI BR cells treated with 6-thio-dG (6dG). (K) The immnohistochemical analysis of AXL was performed in A375 tumors that were treated with the control, 6-thio-dG and Dabrafenib. Supplementary Fig. S3: Related to Fig. 5 (A-C) The heatmaps of two telomere transcriptional gene signatures, two melanoma-specific gene sets and two MAPK pathway-related gene sets in three datasets in which transcriptomes of paired pre- and post-treatment tumor biopsies derived from patients who progressed on MAPKi were profiled. 5 Supplementary Fig. S4: Related to Fig. 5 6 The heatmaps of two telomere transcriptional gene signatures, two melanoma-specific gene sets and two MAPK pathway-related gene sets in paired pre-, on- and post-treatment tumor biopsies derived from 16 patients who were treated with immunotherapies. Supplementary Fig. S5: Related to Fig. 6 (A-E) The heatmaps of RPPA data depicting 30 proteins that were most significantly downregulated in 5 short-term cultures or cell lines derived from immunotherapy-resistant tumors that were treated with 6-thio-dG, including 13-456-3-3 (A), 15-1761-1-2 (B), WM4265-1 (C), WM4265-2 (D) and G43 (E).

Adoptive cell transfer (ACT) immunotherapy has remarkable efficacy against some hematological malignancies. However, its efficacy in solid tumors is limited by the adverse tumor microenvironment (TME) conditions, most notably that acidity inhibits T and natural killer (NK) cell mTOR complex 1 (mTORC1) activity and impairs cytotoxicity. In several reported studies, systemic buffering of tumor acidity enhanced the efficacy of immune checkpoint inhibitors. Paradoxically, we found in a c-Myc-driven hepatocellular carcinoma model that systemic buffering increased tumor mTORC1 activity, negating inhibition of tumor growth by anti-PD1 treatment. Therefore, in this proof-of-concept study, we tested the metabolic engineering of immune effector cells to mitigate the inhibitory effect of tumor acidity while avoiding side effects associated with systemic buffering. We first overexpressed an activated RHEB in the human NK cell line NK-92, thereby rescuing acid-blunted mTORC1 activity and enhancing cytolytic activity. Then, to directly mitigate the effect of acidity, we ectopically expressed acid extruder proteins. Whereas ectopic expression of carbonic anhydrase IX (CA9) moderately increased mTORC1 activity, it did not enhance effector function. In contrast, overexpressing a constitutively active Na(+)/H(+)-exchanger 1 (NHE1; SLC9A1) in NK-92 did not elevate mTORC1 but enhanced degranulation, target engagement, in vitro cytotoxicity, and in vivo antitumor activity. Our findings suggest the feasibility of overcoming the inhibitory effect of the TME by metabolically engineering immune effector cells, which can enhance ACT for better efficacy against solid tumors.

Melanoma is the deadliest of skin cancers and has a high tendency to metastasize to distant organs. Calcium and metabolic signals contribute to melanoma invasiveness; however, the underlying molecular details are elusive. The MCU complex is a major route for calcium into the mitochondrial matrix but whether MCU affects melanoma pathobiology was not understood. Here, we show that MCUA expression correlates with melanoma patient survival and is decreased in BRAF kinase inhibitor-resistant melanomas. Knockdown (KD) of MCUA suppresses melanoma cell growth and stimulates migration and invasion. In melanoma xenografts, MCUA_KD reduces tumor volumes but promotes lung metastases. Proteomic analyses and protein microarrays identify pathways that link MCUA and melanoma cell phenotype and suggest a major role for redox regulation. Antioxidants enhance melanoma cell migration, while prooxidants diminish the MCUA_KD-induced invasive phenotype. Furthermore, MCUA_KD increases melanoma cell resistance to immunotherapies and ferroptosis. Collectively, we demonstrate that MCUA controls melanoma aggressive behavior and therapeutic sensitivity. Manipulations of mitochondrial calcium and redox homeostasis, in combination with current therapies, should be considered in treating advanced melanoma.

Background Melanoma, the deadliest of skin cancers, has a high propensity to form brain metastases that are associated with a markedly worsened prognosis. In spite of recent therapeutic advances, melanoma brain lesions remain a clinical challenge, biomarkers predicting brain dissemination are not clear and differences with other metastatic sites are poorly understood. Methods We examined a genetically diverse panel of human-derived melanoma brain metastasis (MBM) and extracranial cell lines using targeted sequencing, a Reverse Phase Protein Array, protein expression analyses, and functional studies in vitro and in vivo. Results Brain-specific genetic alterations were not detected; however, MBM cells in vitro displayed lower proliferation rates and MBM-specific protein expression patterns associated with proliferation, DNA damage, adhesion, and migration. MBM lines displayed higher levels of RAC1 expression, involving a distinct RAC1-PAK1-JNK1 signaling network. RAC1 knockdown or treatment with small molecule inhibitors contributed to a less aggressive MBM phenotype in vitro, while RAC1 knockdown in vivo led to reduced tumor volumes and delayed tumor appearance. Proliferation, adhesion, and migration were higher in MBM vs nonMBM lines in the presence of insulin or brain-derived factors and were affected by RAC1 levels. Conclusions Our findings indicate that despite their genetic variability, MBM engage specific molecular processes such as RAC1 signaling to adapt to the brain microenvironment and this can be used for the molecular characterization and treatment of brain metastases.

Metastatic melanoma is challenging to clinically address. Although standard-of-care targeted therapy has high response rates in patients with BRAF-mutant melanoma, therapy relapse occurs in most cases. Intrinsically resistant melanoma cells drive therapy resistance and display molecular and biologic properties akin to neural crest-like stem cells (NCLSC) including high invasiveness, plasticity, and self-renewal capacity. The shared transcriptional programs and vulnerabilities between NCLSCs and cancer cells remains poorly understood. Here, we identify a developmental LPAR1-axis critical for NCLSC viability and melanoma cell survival. LPAR1 activity increased during progression and following acquisition of therapeutic resistance. Notably, genetic inhibition of LPAR1 potentiated BRAFi ± MEKi efficacy and ablated melanoma migration and invasion. Our data define LPAR1 as a new therapeutic target in melanoma and highlights the promise of dissecting stem cell–like pathways hijacked by tumor cells. Significance: This study identifies an LPAR1-axis critical for melanoma invasion and intrinsic/acquired therapy resistance.

Physical changes in skin are among the most visible signs of aging. We found that young dermal fibroblasts secrete high levels of extracellular matrix (ECM) constituents, including proteoglycans, glycoproteins, and cartilage-linking proteins. The most abundantly secreted was HAPLN1, a hyaluronic and proteoglycan link protein. HAPLN1 was lost in aged fibroblasts, resulting in a more aligned ECM that promoted metastasis of melanoma cells. Reconstituting HAPLN1 inhibited metastasis in an aged microenvironment, in 3-D skin reconstruction models, and in vivo. Intriguingly, aged fibroblast-derived matrices had the opposite effect on the migration of T cells, inhibiting their motility. HAPLN1 treatment of aged fibroblasts restored motility of mononuclear immune cells, while impeding that of polymorphonuclear immune cells, which in turn affected regulatory T-cell recruitment. These data suggest that although age-related physical changes in the ECM can promote tumor cell motility, they may adversely affect the motility of some immune cells, resulting in an overall change in the immune microenvironment. Understanding the physical changes in aging skin may provide avenues for more effective therapy for older patients with melanoma. Significance: These data shed light on the mechanochemical interactions that occur between aged skin, tumor, and immune cell populations, which may affect tumor metastasis and immune cell infiltration, with implications for the efficacy of current therapies for melanoma. See related commentary by Marie and Merlino, p. 19. This article is highlighted in the In This Issue feature, p. 1

Immunotherapy has revolutionized cancer treatment, but many cancers are not impacted by currently available immunotherapeutic strategies. Here, we investigated inflammatory signaling pathways in neuroblastoma, a classically "cold" pediatric cancer. By testing the functional response of a panel of 20 diverse neuroblastoma cell lines to three different inflammatory stimuli, we found that all cell lines have intact interferon signaling, and all but one lack functional cytosolic DNA sensing via cGAS-STING. However, double-stranded RNA (dsRNA) sensing via Toll-like receptor 3 (TLR3) was heterogeneous, as was signaling through other dsRNA sensors and TLRs more broadly. Seven cell lines showed robust response to dsRNA, six of which are in the mesenchymal epigenetic state, while all unresponsive cell lines are in the adrenergic state. Genetically switching adrenergic cell lines toward the mesenchymal state fully restored responsiveness. In responsive cells, dsRNA sensing results in the secretion of proinflammatory cytokines, enrichment of inflammatory transcriptomic signatures, and increased tumor killing by T cells in vitro. Using single-cell RNA sequencing data, we show that human neuroblastoma cells with stronger mesenchymal signatures have a higher basal inflammatory state, demonstrating intratumoral heterogeneity in inflammatory signaling that has significant implications for immunotherapeutic strategies in this aggressive childhood cancer.

Anti-PD-1 therapy is used as a front-line treatment for many cancers, but mechanistic insight into this therapy resistance is still lacking. Here we generate a humanized (Hu)-mouse melanoma model by injecting fetal liver-derived CD34+ cells and implanting autologous thymus in immune-deficient NOD-scid IL2Rγnull (NSG) mice. Reconstituted Hu-mice are challenged with HLA-matched melanomas and treated with anti-PD-1, which results in restricted tumor growth but not complete regression. Tumor RNA-seq, multiplexed imaging and immunohistology staining show high expression of chemokines, as well as recruitment of FOXP3+ Treg and mast cells, in selective tumor regions. Reduced HLA-class I expression and CD8+/Granz B+ T cells homeostasis are observed in tumor regions where FOXP3+ Treg and mast cells co-localize, with such features associated with resistance to anti-PD-1 treatment. Combining anti-PD-1 with sunitinib or imatinib results in the depletion of mast cells and complete regression of tumors. Our results thus implicate mast cell depletion for improving the efficacy of anti-PD-1 therapy.

The clinical benefit of MAPK pathway inhibition in melanoma patients carrying BRAF mutations is temporal. After the initial response to treatment, the majority of tumors will develop resistance and patients will relapse. Here we demonstrate that the endothelin-endothelin receptor B (ETBR) signaling pathway confers resistance to MAPK pathway inhibitors in BRAF mutated melanoma. MAPK blockade, in addition to being anti-proliferative, induces a phenotypic change which is characterized by increased expression of melanocyte-specific genes including ETBR. In the presence of MAPK inhibitors, activation of ETBR by endothelin enables the sustained proliferation of melanoma cells. In mouse models of melanoma, including patient-derived xenograft models, concurrent inhibition of the MAPK pathway and ETBR signaling resulted in a more effective anti-tumor response compared to MAPK pathway inhibition alone. The combination treatment significantly reduced tumor growth and prolonged survival compared to therapies with MAPK pathway inhibitors alone. The phosphoproteomic analysis revealed that ETBR signaling did not induce resistance towards MAPK pathway inhibitors by restoring MAPK activity, but instead via multiple alternative signaling pathways downstream of the small G proteins GNAq/11. Together these data indicate that a combination of MAPK pathway inhibitors with ETBR antagonists could have a synergistically beneficial effect in melanoma patients with hyperactivated MAPK signaling pathways.

Besides somatic mutations or drug efflux, epigenetic reprogramming can lead to acquired drug resistance. We recently have identified early stress-induced multi-drug tolerant cancer cells termed induced drug-tolerant cells (IDTCs). Here, IDTCs were generated using different types of cancer cell lines; melanoma, lung, breast and colon cancer. A common loss of the H3K4me3 and H3K27me3 and gain of H3K9me3 mark was observed as a significant response to drug exposure or nutrient starvation in IDTCs. These epigenetic changes were reversible upon drug holidays. Microarray, qRT-PCR and protein expression data confirmed the up-regulation of histone methyltransferases (SETDB1 and SETDB2) which contribute to the accumulation of H3K9me3 concomitantly in the different cancer types. Genome-wide studies suggest that transcriptional repression of genes is due to concordant loss of H3K4me3 and regional increment of H3K9me3. Conversely, genome-wide CpG site-specific DNA methylation showed no common changes at the IDTC state. This suggests that distinct histone methylation patterns rather than DNA methylation are driving the transition from parental to IDTCs. In addition, silencing of SETDB1/2 reversed multi drug tolerance. Alterations of histone marks in early multi-drug tolerance with an increment in H3K9me3 and loss of H3K4me3/H3K27me3 is neither exclusive for any particular stress response nor cancer type specific but rather a generic response.

Summary: Therapy of advanced melanoma is changing dramatically. Following mutational and biological subclassification of this heterogeneous cancer, several targeted and immune therapies were approved and increased survival significantly. To facilitate further advancements through pre-clinical in vivo modeling, we have established 459 patient-derived xenografts (PDX) and live tissue samples from 384 patients representing the full spectrum of clinical, therapeutic, mutational, and biological heterogeneity of melanoma. PDX have been characterized using targeted sequencing and protein arrays and are clinically annotated. This exhaustive live tissue resource includes PDX from 57 samples resistant to targeted therapy, 61 samples from responders and non-responders to immune checkpoint blockade, and 31 samples from brain metastasis. Uveal, mucosal, and acral subtypes are represented as well. We show examples of pre-clinical trials that highlight how the PDX collection can be used to develop and optimize precision therapies, biomarkers of response, and the targeting of rare genetic subgroups. : Krepler et al. have established a collection of melanoma patient-derived xenografts (PDX). Melanoma is a very heterogeneous cancer, and this large collection includes even rare subtypes and genetic aberrations in sufficient numbers. Multiple PDX from therapy-resistant patients are characterized and tested in pre-clinical trials for second line therapies. Keywords: melanoma, patient-derived xenografts, targeted therapy, immune checkpoint blockade, melanoma brain metastasis, in vivo models, BRAF inhibitor resistance, ERK inhibitor, MDM2 inhibitor, PI3K beta inhibitor

// Clemens Krepler 1 , Min Xiao 1 , Minu Samanta 1 , Adina Vultur 1 , Hsin-Yi Chen 1 , Patricia Brafford 1 , Patricia I. Reyes-Uribe 1 , Molly Halloran 1 , Thomas Chen 1 , Xu He 1 , Denitsa Hristova 1 , Qin Liu 1 , Ahmed A. Samatar 2 , Michael A. Davies 3 , Katherine L. Nathanson 4 , Mizuho Fukunaga-Kalabis 1 , Meenhard Herlyn 1 and Jessie Villanueva 1 1 The Wistar Institute, Melanoma Research Center, Philadelphia, PA, USA 2 Discovery Oncology Merck Research Laboratories, Boston, MA, USA 3 Melanoma Medical Oncology and Systems Biology University of Texas MD Anderson Cancer Center, Houston, TX, USA 4 Division of Medical Genetics and The Abramson Cancer Center, University of Pennsylvania School of Medicine, Philadelphia PA, USA Correspondence to: Jessie Villanueva, email: // Keywords : melanoma, targeted therapy resistance, ERK, BRAF, Notch Received : February 29, 2016 Accepted : September 12, 2016 Published : September 16, 2016 Abstract The discovery of activating BRAF mutations in approximately 50% of melanomas has led to the development of MAPK pathway inhibitors, which have transformed melanoma therapy. However, not all BRAF-V600E melanomas respond to MAPK inhibition. Therefore, it is important to understand why tumors with the same oncogenic driver have variable responses to MAPK inhibitors. Here, we show that concurrent loss of PTEN and activation of the Notch pathway is associated with poor response to the ERK inhibitor SCH772984, and that co-inhibition of Notch and ERK decreased viability in BRAF-V600E melanomas. Additionally, patients with low PTEN and Notch activation had significantly shorter progression free survival when treated with BRAF inhibitors. Our studies provide a rationale to further develop combination strategies with Notch antagonists to maximize the efficacy of MAPK inhibition in melanoma. Our findings should prompt the evaluation of combinations co-targeting MAPK/ERK and Notch as a strategy to improve current therapies and warrant further evaluation of co-occurrence of aberrant PTEN and Notch activation as predictive markers of response to therapy.

// Batool Shannan 1, 2 , Andrea Watters 1 , Quan Chen 1 , Stefan Mollin 3 , Markus Dorr 3 , Eric Meggers 3 , Xiaowei Xu 4 , Phyllis A. Gimotty 5 , Michela Perego 1 , Ling Li 1 , Joseph Benci 1 , Clemens Krepler 1 , Patricia Brafford 1 , Jie Zhang 6 , Zhi Wei 6 , Gao Zhang 1 , Qin Liu 1 , Xiangfan Yin 1 , Katherine L. Nathanson 4 , Meenhard Herlyn 1, * , Adina Vultur 1, * 1 Program of Cellular and Molecular Oncogenesis, Melanoma Research Center, The Wistar Institute, Philadelphia, PA, USA 2 Department of Dermatology, University Hospital Essen, Essen, Germany 3 Department of Chemistry, University of Marburg, Marburg, Germany 4 Abramson Cancer Center, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA 5 Department of Biostatistics and Epidemiology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA 6 Department of Computer Science, New Jersey Institute of Technology, Newark, NJ, USA * Co-senior authors Correspondence to: Adina Vultur, email: avultur@wistar.org Keywords: melanoma, PIM kinases, SGI-1776, organometallics, therapy Received: October 04, 2015 Accepted: June 06, 2016 Published: July 19, 2016 ABSTRACT Therapeutic strategies for the treatment of metastatic melanoma show encouraging results in the clinic; however, not all patients respond equally and tumor resistance still poses a challenge. To identify novel therapeutic targets for melanoma, we screened a panel of structurally diverse organometallic inhibitors against human-derived normal and melanoma cells. We observed that a compound that targets PIM kinases (a family of Ser/Thr kinases) preferentially inhibited melanoma cell proliferation, invasion, and viability in adherent and three-dimensional (3D) melanoma models. Assessment of tumor tissue from melanoma patients showed that PIM kinases are expressed in pre- and post-treatment tumors, suggesting PIM kinases as promising targets in the clinic. Using knockdown studies, we showed that PIM1 contributes to melanoma cell proliferation and tumor growth in vivo ; however, the presence of PIM2 and PIM3 could also influence the outcome. The inhibition of all PIM isoforms using SGI-1776 (a clinically-available PIM inhibitor) reduced melanoma proliferation and survival in preclinical models of melanoma. This was potentiated in the presence of the BRAF inhibitor PLX4720 and in the presence of PI3K inhibitors. Our findings suggest that PIM inhibitors provide promising additions to the targeted therapies available to melanoma patients.

Targeting multiple components of the MAPK pathway can prolong the survival of patients with BRAFV600E melanoma. This approach is not curative, as some BRAF-mutated melanoma cells are intrinsically resistant to MAPK inhibitors (MAPKi). At the systemic level, our knowledge of how signaling pathways underlie drug resistance needs to be further expanded. Here, we have shown that intrinsically resistant BRAF-mutated melanoma cells with a low basal level of mitochondrial biogenesis depend on this process to survive MAPKi. Intrinsically resistant cells exploited an integrated stress response, exhibited an increase in mitochondrial DNA content, and required oxidative phosphorylation to meet their bioenergetic needs. We determined that intrinsically resistant cells rely on the genes encoding TFAM, which controls mitochondrial genome replication and transcription, and TRAP1, which regulates mitochondrial protein folding. Therefore, we targeted mitochondrial biogenesis with a mitochondrium-targeted, small-molecule HSP90 inhibitor (Gamitrinib), which eradicated intrinsically resistant cells and augmented the efficacy of MAPKi by inducing mitochondrial dysfunction and inhibiting tumor bioenergetics. A subset of tumor biopsies from patients with disease progression despite MAPKi treatment showed increased mitochondrial biogenesis and tumor bioenergetics. A subset of acquired drug-resistant melanoma cell lines was sensitive to Gamitrinib. Our study establishes mitochondrial biogenesis, coupled with aberrant tumor bioenergetics, as a potential therapy escape mechanism and paves the way for a rationale-based combinatorial strategy to improve the efficacy of MAPKi.

Purpose: To test second-line personalized medicine combination therapies, based on genomic and proteomic data, in patient-derived xenograft (PDX) models. Experimental Design: We established 12 PDXs from BRAF inhibitor–progressed melanoma patients. Following expansion, PDXs were analyzed using targeted sequencing and reverse-phase protein arrays. By using multi-arm preclinical trial designs, we identified efficacious precision medicine approaches. Results: We identified alterations previously described as drivers of resistance: NRAS mutations in 3 PDXs, MAP2K1 (MEK1) mutations in 2, BRAF amplification in 4, and aberrant PTEN in 7. At the protein level, re-activation of phospho-MAPK predominated, with parallel activation of PI3K in a subset. Second-line efficacy of the pan-PI3K inhibitor BKM120 with either BRAF (encorafenib)/MEK (binimetinib) inhibitor combination or the ERK inhibitor VX-11e was confirmed in vivo. Amplification of MET was observed in 3 PDX models, a higher frequency than expected and a possible novel mechanism of resistance. Importantly, MET amplification alone did not predict sensitivity to the MET inhibitor capmatinib. In contrast, capmatinib as single agent resulted in significant but transient tumor regression in a PDX with resistance to BRAF/MEK combination therapy and high pMET. The triple combination capmatinib/encorafenib/binimetinib resulted in complete and sustained tumor regression in all animals. Conclusions: Genomic and proteomic data integration identifies dual-core pathway inhibition as well as MET as combinatorial targets. These studies provide evidence for biomarker development to appropriately select personalized therapies of patients and avoid treatment failures. Clin Cancer Res; 22(7); 1592–602. ©2015 AACR. See related commentary by Hartsough and Aplin, p. 1550

Purpose: Telomerase promoter mutations are highly prevalent in human tumors including melanoma. A subset of patients with metastatic melanoma often fail multiple therapies, and there is an unmet and urgent need to prolong disease control for those patients. Experimental Design: Numerous preclinical therapy-resistant models of human and mouse melanoma were used to test the efficacy of a telomerase-directed nucleoside, 6-thio-2′-deoxyguanosine (6-thio-dG). Integrated transcriptomics and proteomics approaches were used to identify genes and proteins that were significantly downregulated by 6-thio-dG. Results: We demonstrated the superior efficacy of 6-thio-dG both in vitro and in vivo that results in telomere dysfunction, leading to apoptosis and cell death in various preclinical models of therapy-resistant melanoma cells. 6-thio-dG concomitantly induces telomere dysfunction and inhibits the expression level of AXL. Conclusions: In summary, this study shows that indirectly targeting aberrant telomerase in melanoma cells with 6-thio-dG is a viable therapeutic approach in prolonging disease control and overcoming therapy resistance. Clin Cancer Res; 24(19); 4771–84. ©2018 AACR. See related commentary by Teh and Aplin, p. 4629

Autophagy mediates resistance to various anticancer agents. In melanoma, resistance to targeted therapy has been linked to expression of Wnt5A, an intrinsic inhibitor of β-catenin, which also promotes invasion. In this study, we assessed the interplay between Wnt5A and autophagy by combining expression studies in human clinical biopsies with functional analyses in cell lines and mouse models. Melanoma cells with high Wnt5A and low β-catenin displayed increased basal autophagy. Genetic blockade of autophagy revealed an unexpected feedback loop whereby knocking down the autophagy factor ATG5 in Wnt5Ahigh cells decreased Wnt5A and increased β-catenin. To define the physiologic relevance of this loop, melanoma cells with different Wnt status were treated in vitro and in vivo with the potent lysosomotropic compound Lys05. Wnt5Ahigh cells were less sensitive to Lys05 and could be reverted by inducing β-catenin activity. Our results suggest the efficacy of autophagy inhibitors might be improved by taking the Wnt signature of melanoma cells into account. Cancer Res; 77(21); 5873–85. ©2017 AACR.